drivers/clocksource/clksrc-dbx500-prcmu.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * Copyright (C) ST-Ericsson SA 2011
0004  *
0005  * Author: Mattias Wallin <mattias.wallin@stericsson.com> for ST-Ericsson
0006  * Author: Sundar Iyer for ST-Ericsson
0007  * sched_clock implementation is based on:
0008  * plat-nomadik/timer.c Linus Walleij <linus.walleij@stericsson.com>
0009  *
0010  * DBx500-PRCMU Timer
0011  * The PRCMU has 5 timers which are available in a always-on
0012  * power domain.  We use the Timer 4 for our always-on clock
0013  * source on DB8500.
0014  */
0015 #include <linux/of.h>
0016 #include <linux/of_address.h>
0017 #include <linux/clockchips.h>
0018
0019 #define RATE_32K        32768
0020
0021 #define TIMER_MODE_CONTINUOUS   0x1
0022 #define TIMER_DOWNCOUNT_VAL 0xffffffff
0023
0024 #define PRCMU_TIMER_REF     0
0025 #define PRCMU_TIMER_DOWNCOUNT   0x4
0026 #define PRCMU_TIMER_MODE    0x8
0027
0028 static void __iomem *clksrc_dbx500_timer_base;
0029
0030 static u64 notrace clksrc_dbx500_prcmu_read(struct clocksource *cs)
0031 {
0032     void __iomem *base = clksrc_dbx500_timer_base;
0033     u32 count, count2;
0034
0035     do {
0036         count = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT);
0037         count2 = readl_relaxed(base + PRCMU_TIMER_DOWNCOUNT);
0038     } while (count2 != count);
0039
0040     /* Negate because the timer is a decrementing counter */
0041     return ~count;
0042 }
0043
0044 static struct clocksource clocksource_dbx500_prcmu = {
0045     .name       = "dbx500-prcmu-timer",
0046     .rating     = 100,
0047     .read       = clksrc_dbx500_prcmu_read,
0048     .mask       = CLOCKSOURCE_MASK(32),
0049     .flags      = CLOCK_SOURCE_IS_CONTINUOUS | CLOCK_SOURCE_SUSPEND_NONSTOP,
0050 };
0051
0052 static int __init clksrc_dbx500_prcmu_init(struct device_node *node)
0053 {
0054     clksrc_dbx500_timer_base = of_iomap(node, 0);
0055
0056     /*
0057      * The A9 sub system expects the timer to be configured as
0058      * a continuous looping timer.
0059      * The PRCMU should configure it but if it for some reason
0060      * don't we do it here.
0061      */
0062     if (readl(clksrc_dbx500_timer_base + PRCMU_TIMER_MODE) !=
0063         TIMER_MODE_CONTINUOUS) {
0064         writel(TIMER_MODE_CONTINUOUS,
0065                clksrc_dbx500_timer_base + PRCMU_TIMER_MODE);
0066         writel(TIMER_DOWNCOUNT_VAL,
0067                clksrc_dbx500_timer_base + PRCMU_TIMER_REF);
0068     }
0069     return clocksource_register_hz(&clocksource_dbx500_prcmu, RATE_32K);
0070 }
0071 TIMER_OF_DECLARE(dbx500_prcmu, "stericsson,db8500-prcmu-timer-4",
0072                clksrc_dbx500_prcmu_init);